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Tuning the reactivity of Al-Ni by fine coating of halogen-containing energetic composites

Defence Technology（防务技术） 2022年第10期18卷 1810-1821页

作者： Su-lan Yang Ke-juan Meng Wu-xi Xie Hong-qi Nie Qi-Long Yan Science and Technology on combustion Internal Flow and Thermo-Structure LaboratoryNorthwestern Polytechnical UniversityXi'an710072China b Xi'an Modern Chemistry Research institute Xi'an710065China

In this paper,various core-shell structured Al—Ni@ECs composites have been prepared by a spray-drying *** involved ECs refer to the energetic composites(ECs)of ammonium perchlorate/nitrocellulose(AP/NC,NA)and polyvinylidene fluoride/hexanitrohexaazaisowurtzitane(PVDF/CL-20,PC).Two Al—Ni mixtures were prepared at atomic ratios of 1:1 and 1:3 and named as Al/Ni and Al/3Ni,*** thermal reactivity and combustion behaviors of Al—Ni@ECs composites have been comprehensively *** showed that the reactivity and combustion performance of Al—Ni could be enhanced by introducing both NA and PC energetic *** which the Al/Ni@NA composite exhibited higher reactivity and improved combustion *** measured flame propagation rate(v=20.6 mm/s),average combustion wave temperature(T_(max)=1567.0°C)and maximum temperature rise rate(γ_(t)=1633.6°C/s)of Al/Ni@NA are higher than that of the Al/Ni(v=15.8 mm/s,T_(max)=858.0°C,andγ_(t)=143.5°C/s).The enhancement in combustion properties could be due to presence of the acidic gaseous products from ECs,which could etch the Al_(2)O_(3)shell on the surface of Al particles,and make the inner active Al to be easier transported,so that an intimate and faster intermetallic reaction between Al and Ni would be ***,the morphologies and chemical compositions of the condensed combustion products(CCPs)of Al—Ni@ECs composites were found to be different depending on the types of *** compositions of CCPs are dominated with the Al—Ni intermetallics,combining with a trace amount of Al_(5)O_(6)N and Al_(2)O_(3).

关键词： Arrested high energy ball milling Intermetallic alloy combustion performance Energetic composites Reactivity control

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Fabrication and characterization of multi-scale coated boron powders with improved combustion performance:A brief review

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Defence Technology（防务技术） 2024年第1期31卷 27-40页

作者： Rui Liu Danfeng Yang Kunyu Xiong Ying-Lei Wang Qi-Long Yan Science and Technology on combustion Internal Flow and Thermo-structure LaboratoryNorthwestern Polytechnical UniversityXi'an710072China Xi'an Modern Chemistry Research institute Xi'an710065China

Boron has high mass and volume calorific values,but it is difficult to ignite and has low combustion *** literature review summarizes the strategies that are used to solve the above-mentioned problems,which include coatings of boron by using fluoride compounds,energetic composites,metal fuels,and metal *** techniques include recrystallization,dual-solvent,phase transfer,electrospinning,*** one of the effective coating agents,the fluorine compounds can react with the oxide shell of boron *** comparison,the energetic composites can effectively improve the flame temperature of boron powder and enhance the evaporation efficiency of oxide film as a condensed *** and metal oxides would react with boron powder to form metal borides with a lower ignition point,which could reduce its ignition temperature.

关键词： Boron powder coating Structure and morphology Condensed phase thermal reaction Ignition and combustion

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engine performance and combustion characteristics of a direct injection compression ignition engine fueled waste cooking oil synthetic diesel

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International Journal of Coal Science & Technology 2020年第3期7卷 560-570页

作者： Thanh Viet Nguyen Khanh Duc Nguyen Nang Xuan Ho Vinh Duy Nguyen Department of internal combustion engine School of Transportation EngineeringHanoi University of Science and TechnologyHanoiViet Nam Faculty of Vehicle and Energy engineering Phenikaa UniversityYen NghiaHa-Dong DistrictHanoiViet Nam

Biodiesels produced from various feedstocks have been considered as alternative fuels used in internal combustion engines without major *** research focuses on producing biodiesel from waste cooking oil(WCOSD)by the catalytic cracking method using MgO as the catalyst and comparing the engine operating characteristics of the test engine when using WCOSD and traditional diesel(CD)as test *** a result,the brake power of the test engine fueled WCOSD,and traditional diesel is ***,the engine fuel consumption in the case of using WCOSD is slight increases in some operating ***,the nitrogen oxides emissions of the test engine fueled WCOSD are higher than those of CD at all tested *** trend is opposite for hydrocarbon emission as the HC emission of the engine fueled by WCOSD reduces 26.3%on *** smoke emission of the test engine in case of using WCOSD is lower 17%on average than that of ***,the carbon monoxide emissions are lower at the low and medium loads and higher at the full *** results show that the new biodiesel has the same characteristics as those of commercial biodiesel and can be used as fuel for diesel engines.

关键词： Feedstock Waste cooking oil engine characteristics Exhaust missions Ignition timing Fuel consumption

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Explore artificial neural networks for solving complex hydrocarbon chemistry in turbulent reactive flows

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Fundamental Research 2022年第4期2卷 595-603页

作者： Jian An Fei Qin Jian Zhang Zhuyin Ren Institte for Aero engine Tsinghua UniversitBejing 100084China Seience and Technology on combustion Internal Flow and Thermal-structure LaboratoryNorthwesterm Polytechnical UniversityXi'an 710072China

Global warming caused by the use of fossil fuels is a common concern of the world *** is of practical importance to conduct in-depth fundamental research and optimal design for modern engine combustors through However,complex hydrocarbon chemistry,an indispensable component for predictive modeling,is computahigh-fidelity computational fluid dynamics(CFD),so as to achieve energy conservation and emission *** demanding,Its application in simulation-based design optimization,although desirable,is quite *** address this challenge,we propose a methodology for representing complex chemistry with artificial neural networks(ANNs),which are trained with a comprehensive sample dataset generated by the Latin hypercube sampling(LHS)*** a given chemical kinetic mechanism,the thermochemical sample data is able to cover the whole accessible pressure/temperature/species space in various turbulent *** ANN-based model consists of two different layers:the self-organizing map(SOM)and the back-propagation neural network(BPNN).The methodology is demonstrated to represent a 30-species methane chemical *** obtained ANN model is applied to simulate both a non-premixed turbulent flame(DLR_A)and a partially premixed turbulent flame(Flame D)to validate its applicability for different *** show that the ANN-based chemical kinetics can reduce the computational cost by about two orders of magnitude without loss of accuracy,The proposed methodology can successfully construct an ANN-based chemical mechanism with significant ffciency gain and a broad scope of applicability,and thus holds a great potential for complex hydrocarbon fuels.

关键词： Chemical kinetics Turbulent combustion Artificial neural network Machine learning Numerical simulation

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Experimental research on rotating detonation with liquid hypergolic propellants

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Chinese Journal of Aeronautics 2018年第12期31卷 2199-2205页

作者： Shuaijie XUE Hongjun LIU Lixin ZHOU Weidong YANG Hongbo HU Yu YAN Science and Technology on Liquid Rocket engine Laboratory Xi'an Aerospace Propulsion Institute

This paper describes experimental research into the initiation and propagation of rotating detonation for liquid Nitrogen TetrOxide(NTO) and liquid MonoMethylHydrazine(MMH).An annular rocket-type combustor without nozzle was designed to investigate detonation combustion. The propellants were injected through unlike impingement injectors. The combustion flame fronts and pressure waves were detected using optical diagnostics and dynamic pressure sensors,respectively. The propagation of rotating detonation was established spontaneously by increasing the mass flow rate of propellants. The velocity of propagation of the flame fronts and pressure waves was nearly equal and reaches supersonic speed. Two different detonation combustion patterns are present, single wave mode and double waves mode. And in double waves mode, the two detonation waves are always counter-rotating. The possibility of rotating detonation initiation in a combustor with nozzle was also checked. Stable rotating detonation can be initialized and sustained at similar operating conditions.

关键词： Hypergolic Initiation Liquid propellant Nozzle Rotating detonation

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Periodic atomization characteristics of an impinging jet injector element modulated by Klystron effect

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Chinese Journal of Aeronautics 2018年第10期31卷 1973-1984页

作者： Anlong YANG Bin LI Shangrong YANG Yunfei XU Longfei LI Science and Technology on Liquid Rocket engine Laboratory Xi'an Aerospace Propulsion Institute

An experimental study on the Klystron effect of periodic injection modulated by pressure drop fluctuations on subsequent atomization is conducted. Time-resolved atomization backlit images and atomization Mie scatter images are captured by using the high speed camera. It is found that periodicity of forced atomization relies on pressure drop fluctuation amplitude and phase differences between atomization and pressure drop fluctuations relate to fluctuation frequencies. This feature of periodic atomization induced by Klystron effect corresponds to periodicities and high amplitudes of pressure fluctuations in unstable combustion chambers and chaos and low amplitudes of pressure fluctuations in stable combustions chambers. Drastically periodic varying of gross surface area of droplets with time was shown in Mie scatter images. The importance of periodic impinging jet atomization modulated by pressure drop fluctuations for acoustic liquid propellant combustion instabilities is illustrated.

关键词： Atomization combustion stability Impinging jet injector Klystron effect Liquid rocket engine Mie scatter

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Degradation prediction of proton exchange membrane fuel cell stack using semi-empirical and data-driven methods

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Energy and AI 2023年第1期11卷 1-11页

作者： Yupeng Wang Kangcheng Wu Honghui Zhao Jincheng Li Xia Sheng Yan Yin Qing Du Bingfeng Zu Linghai Han Kui Jiao State Key Laboratory of engines Tianjin University135 Yaguan RoadTianjin300350China Powertrain Department General R&D InstituteFAWNo.1 Xinhongqi StreetChangchunJilin 130013China internal combustion engine Research institute Tianjin University92 Weijin RoadTianjin300072China

Degradation prediction of proton exchange membrane fuel cell(PEMFC)stack is of great significance for improving the rest useful *** this study,a PEMFC system including a stack of 300 cells and subsystems has been tested under semi-steady operations for about 931 ***,two different models are respectively established based on semi-empirical method and data-driven method to investigate the degradation of stack *** is found that the root mean square error(RMSE)of the semi-empirical model in predicting the stack voltage is around 1.0 V,while the predicted voltage has no local dynamic characteristics,which can only reflect the overall degradation trend of stack *** RMSE of short-term voltage degradation predicted by the DDM can be less than 1.0 V,and the predicted voltage has accurate local variation ***,for the long-term prediction,the error will accumulate with the iterations and the deviation of the predicted voltage begins to fluctuate gradually,and the RMSE for the long-term predictions can increase to 1.63 *** on the above characteristics of the two models,a hybrid prediction model is further *** prediction results of the semi-empirical model are used to modify the input of the data-driven model,which can effectively improve the oscillation of prediction results of the data-driven model during the long-term *** is found that the hybrid model has good error distribution(RSEM=0.8144 V,R2=0.8258)and local performance dynamic characteristics which can be used to predict the process of long-term stack performance degradation.

关键词： Proton exchange membrane fuel cell system Data-driven method Semi-empirical equation Degradation experiments

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Periodic atomization characteristics of simplex swirl injector induced by klystron effect

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Chinese Journal of Aeronautics 2018年第5期31卷 1066-1074页

作者： Anlong YANG Shangrong YANG Yunfei XU Longfei LI Science and Technology on Liquid Rocket engine Laboratory Xi'an Aerospace Propulsion Institute

The atomization dynamic characteristics of a simplex swirl injector was investigated experimentally by using a hydrodynamic mechanical pulsator and the shadow photography technique. The frequency response characteristics of the fluid film and atomization fluctuations and their correlations with pressure fluctuations were obtained by using an in-house code of image processing. It is demonstrated that the klystron effect induced by periodic pressure fluctuations results in periodic liquid film fluctuation with large amplitudes, periodic superposition of droplets and reduction of the breakup length. It was found that the atomization of the simplex swirl injector only responds to the pressure fluctuation in frequency range approximately from 0 to 300 Hz, and it is particularly sensitive to pressure fluctuations at frequencies from 100 to 200 Hz. According to this experiment, the responsive frequency limitation is merely affected by injector configuration, rather than the supply line.

关键词： Atomization combustion stability Klystron effect Liquid rocket engine Simplex swirl injector

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Unified gas-kinetic particle method for dilute granular flow and its application in a solid jet

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Acta Mechanica Sinica 2020年第1期36卷 22-34页

作者： Zhao Wang Hong Yan Yangtze River Delta Research institute of NPU Northwestern Polytechnical UniversityTaicang215400JiangsuChina Shaanxi Key Laboratory of internal Aerodynamics in Aero-engine Xi’an710072China

Because of its complexity,the problem of multiscale structure in granular flow has been receiving increasing *** this work,in order to conduct an in-depth exploration of the multiscale structure,a unified gas-kinetic particle(UGKP)method suitable for granular flow is constructed,in which the collision damping term and return-to-isotropy term are added to characterize the collision between *** the above two collision terms,the former characterizes the inelastic collision of particles,while the latter emphasizes the importance of the isotropic distribution of particles,which makes the results more reliable and *** construction of unified gas-kinetic schemes(UGKS)for granular flow has been reported in previous ***,because of the need for discrete velocity space,the calculation size is quite large,making it impossible to use UGKS directly to investigate the multiscale ***,for UGKP,the flux contributed by particle free transport is calculated by free-streaming particles instead of discrete velocity space so that the corresponding calculation is much smaller than *** validity of the method is verified by numerical simulation of the solid jet compared with the particle-in-cell(PIC)*** addition,since the sampled particles are used to obtain the flux contributed by the free transport,UGKP is more efficient than UGKS for solving multiscale problems.

关键词： Granular flow UGKP Multiscale Return-to-isotropy

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A forced ignition probability analysis method using kernel formation analysis with turbulent transport and Lagrangian flame particle tracking

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Chinese Journal of Aeronautics 2021年第4期34卷 403-415页

作者： Qing XIE Zhuyin REN Ke WANG Hongjun LIN Shoutang SHANG Wei XIAO School of Aerospace engineering Tsinghua UniversityBeijing 100084China institute for Aero engine Tsinghua UniversityBeijing 100084China Aero engine Academy of China Beijing 101300China AECC Shenyang engine Research institute Shenyang 110000China AECC Hunan Aviation Powerplant Research institute Zhuzhou 412000China

A forced ignition probability analysis method is developed for turbulent combustion,in which kernel formation is analyzed with local kernel formation criteria,and flame propagation and stabilization are simulated with Lagrangian flame particle *** kernel formation,the effect of turbulent scalar transport on flammability is modelled through the incorporation of turbulenceinduced diffusion in a spherically outwardly propagating flame kernel *** dependence of flammability limits on turbulent intensities is tabulated and serves as the flammability criterion for kernel *** Lagrangian flame particle tracking,flame particles are tracked in a structured grid with flow fields being interpolated from a Computational Fluid Dynamics(CFD)*** particle velocity follows a Langevin model consisting of a linear drift and an isotropic diffusion *** Karlovitz number is employed for the extinction criterion,which compares chemical and turbulent *** integration of the above two-step analysis approach with non-reacting CFD is achieved through a general interpolation interface suitable for general unstructured CFD *** method is demonstrated for a methane/air bluff-body flame,in which flow and fuel/air mixing characteristics are extracted from a non-reacting *** show that the computed ignition probability map agrees qualitatively with experimental results.A reduction of the ignition probability in the recirculation zone and a high ignition probability on the shear layer of the recirculation zone near the mean stoichiometric surface are well *** tools can facilitate optimization of spark placement and offer insights into ignition processes.

关键词： Bluff-body stabilized flame Igniting process Ignition criterion Ignition probability Lagrangian particle tracking

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